A typical semiconductor device includes a die pad, a semiconductor chip arranged on the die pad, leads arranged on the periphery of the die pad, and wires connecting the semiconductor chip and the leads with one another.
When extending the wires, normal bonding of bonding (first bonding) the wires to the semiconductor chip in advance and subsequently bonding (second bonding) the same to the leads is performed in general. In a case where a difference in elevation between portions (pads) of the semiconductor chip to which the wires are connected and the leads is relatively large, however, it is difficult to excellently bond the wires to the leads, and hence the so-called reverse bonding is performed. In the reverse bonding, the wires are first-bonded to the leads, and second-bonded to the semiconductor chip.
FIG. 34 is a schematic side elevational view of a semiconductor device in which a wire is extended by reverse bonding.
The rear surface of a semiconductor chip 201 is bonded to the upper surface of a die pad 202 in a state upwardly directing the front surface which is an element forming surface. A pad 203 is arranged on a peripheral edge portion of the front surface of the semiconductor chip 201. A wire 205 is extended between the pad 203 and the upper surface of a lead 204 arranged on the periphery of the die pad 202.
In wire bonding, the lead 204 is pressed by a press plate 208, in order to fix the die pad 202 and the lead 204 to a wire bonder. The press plate 208 is brought into contact with a position at a small interval from a bonded position of the wire 205 (ball portion 206) on the upper surface of the lead 204 on a side opposite to the semiconductor chip 201. Then, an FAB (Free Air Ball) is formed on a forward end portion of the wire 205 held in a capillary C (shown by broken lines) of the wire bonder, and the FAB is bonded to the upper surface of the lead 204. Thereafter the capillary C is moved toward the pad 203, and the wire 205 is pressed against the pad 203, and further rent away. Thus, the wire 205 is extended between the pad 203 and the lead 204. The wire 205 extended by the reverse bonding has the ball portion 206 in the form of a round rice cake on the lead 204, and has a stitch portion 207 wedged in side elevational view on the pad 203.
A resin-sealed semiconductor device has a structure obtained by sealing a semiconductor chip with a resin package along with a lead frame. The lead frame is formed by punching a metal thin plate, and includes an island (die pad) and a plurality of leads arranged on the periphery of the island. The semiconductor chip is die-bonded to the upper surface of the island, and electrically connected with each lead by a bonding wire extended between the front surface thereof an each lead.
For the die bonding of the semiconductor chip to the island, a pasty bonding agent such as solder paste is employed, for example. After the pasty bonding agent is applied to the upper surface of the island, the semiconductor chip is arranged on the bonding agent, and a load is applied to the semiconductor chip. Thus, the bonding agent is spread between the semiconductor chip and the island, the semiconductor chip and the island are bonded to each other, and the die bonding of the semiconductor chip to the island is achieved.